Questioning Broker’s honesty

Hi all. Will try to keep this as short as possible.

I have just received a copy of my latest mortgage, the fourth mortgage that I've done through this particular broker.

He has always been really slack with communication but I've stuck with him as he knows me and my situation so that has made things a little less complicated.

The issue I am having at the moment comes with a recent construction loan. The land portion of the loan settled a couple of months ago.

Regarding the total construction costs, I instructed the Broker to keep LVR under 87.99 to limit the amount of LMI payable. He sat down and did the figures and we got the LVR down to 87.03% which went onto the application and was signed by me. In this instance, the LVR was lowered by adding $15,000 to the value of the land that I purchased a few months prior, and the value nominated for the land was quite reasonable.

The broker then called me 2 weeks later to say that the Valuer had agreed to the land value that I had nominated and that all was good.

Another week goes by and I receive an SMS from him saying the 'Val had been put through, it is a good val at 89%'.

I Immediately wrote back and questioned if 89% was the LVR of 87.03% + LMI, to which he replied " I would assume so, I will find out and get back to you".

A week goes by without hearing a thing and then I receive a message from him saying it had been signed off by the bank and that the Mortgage docs were on there way to me. I again messaged him back asking him did he sort out the LVR issue. He did not reply.

The mortgage docs arrived and showed LVR at 90.07% which makes for a substantially higher premium. They also show the land value as the purchase price and NOT the purchase value + $15,000 as nominated on the application, this is despite the broker telling me that the Valuer had agreed to it.

I immediately called the broker thinking that this was a mistake. He then advised me that the Valuer did value it at the higher value, but then lowered it back to the value of the purchase price. This seemed strange to me. He also advised me that the construction portion of the loan was reduced by $5000 as the valuer thinks it could be done cheaper. The construction costs are already very conservative and the home is being built with funds totaling approx 10% less than other comparable sales in the street so once again I question this. 

I then wrote a letter with supporting data showing recent land and property sales within the area hoping to contest the valuation. He informs me that he will approach the lender with this data and "see what they say". Despite the data supporting my claim, he calls me last night and states that he has spoken to the company that provides the LMI (QBE) and they will not increase the value of the property to reflect it's true market value as the land purchase was recent, and that they will only go off the purchase price. 

The questions I have are:

-Do brokers earn any commission/kickback based on LVR? 

-Are the insurers really able to set their own guidelines for determining property values?

-How could a property be valued at a certain rate and then devalued a week or so later, despite property sales data supporting the higher value?

-I've never heard of construction costs being lowered by a valuer. Is this normal?

-Where do I go from here?

I cannot understand how an insurer can influence the valuation report as it would obviously be in their interest to keep the value low to increase the LVR and therate of LMI and this seems to be a massive conflict of interest. This is why I have trouble believing the broker.

Also seems strange that the land value would be based on the  outcome of a successfully negotiated price instead of it's actual market value.

Can any body provide any insight or advice?

Thanks so much.